Power Loss Minimization in Smart Transformer Enabled Low Voltage Islanded Meshed Hybrid Microgrid

Abstract

The smart transformer (ST) offers several features in a hybrid microgrid due to the presence of both ac and dc links while providing various power flow paths. For ST based meshed microgrid, continuous operation is highly important and one of the effective ways to achieve it is by minimizing line losses. This paper proposes a power loss minimization strategy which is specific for an ST based islanded meshed hybrid microgrid. In such an islanded system, a battery energy storage system (BESS) is used for maintaining the low voltage (LV) dc bus voltage of ST. The hybrid microgrid consists of renewable energy sources, electric vehicles (EV) charging stations, storage, etc. The minimization of total distribution line power loss is chosen as an objective function for optimization problem. The active power references of distributed generation converters and charge or discharge schedules of EVs are optimally controlled using genetic algorithm while satisfying the various constraints of the system. Further, a smart LV load shedding is also incorporated to the power management. This is activated on crossing the lower critical state of charge of the BESS. It is used as a final measure to increase BESS discharge time resulting in prolonged operation of the islanded system. Simulation and experimental results verify the performance of the proposed scheme. For the various cases considered, the proposed system is compared with conventional power management strategies. It was observed that while in a particular case, the conventional method incurred 1.337 kW losses, the proposed method was able to reduce the line losses to 1.0487 kW. This shows a 22% reduction in line losses with proposed method as compared to conventional method.

Keywords

• Battery energy storage system (BESS)
• electric vehicle
• islanding
• meshed grid
• smart transformer (ST)